Cook over medium heat until it begins to simmer and thickens to a pale beige paste

Slowly whisk the milk into the roux

Continue to whisk until the sauce has no lumps and is the consistency of thick cream

Scrape the vanilla seeds into the warm sauce with a small pinch of salt

Set aside to cool (see note)

Preheat the oven to 325°f convection or 350°f regular.

Lightly butter a 2 quart casserole dish

Cream the cream cheese and sugar in a mixing bowl

Scrape the bowl

Add the eggs, one at a time, scraping the bowl after each egg

Add the cooled white sauce to the cream cheese mixture

Add the cooked pasta and the blueberries to the batter

Pour the batter into the casserole dish

Combine the Panko bread crumbs and 1/4 cup sugar

Sprinkle the topping over the custard

Bake until golden brown, slightly puffed, and the custard is set in the center

Best eaten warm

Notes
Make sure to cook the macaroni "al dente". Leaving the pasta slightly undercooked will allow it to absorb the sauce as it bakes.
If you combine the white sauce with the cream cheese mixture while the sauce is very hot the mixture will look curdled. Allow the sauce to cool to a very slightly warm or room temperature.
Just like savory macaroni and cheese, this is best still warm from the oven. Leftovers can be refrigerated and re-warmed.